| Named By: | Charles Doolittle Walcott in 1911 |
| Time Period: | Cambrian, 520-505 Ma |
| Location: | Worldwide distribution, but particularly well-known from Canada, British Columbia - Burgess shale. Also, China - Kaili Formation, Australia - Emu Bay Shale, Czech Republic - Buchava Formation |
| Size: | Varying sizes from 3.4 to 50.8 millimetres |
| Diet: | Bottom feeder |
| Fossil(s): | Hundreds of known specimens, but sometimes only the spines are recovered |
| Classification: | | Animalia | Lophotrochozoa | |
Wiwaxia is a genus of soft-bodied animals that were covered in carbonaceous scales and spines. Wiwaxia fossils - mainly isolated scales, but sometimes complete, articulated fossils - are known from early Cambrian and middle Cambrian fossil deposits across the globe. The living animal would have measured up to 5 cm (2 inch) when fully grown, although a range of juvenile specimens are known, the smallest being 2 millimetres (0.079 in) long.
Wiwaxia's affinity has been a matter of debate: researchers were long split between two possibilities. On the one hand, its rows of scales looked superficially similar to certain scale worms (annelids); conversely, its mouthparts and general morphology suggested a relationship to the shell-less molluscs. More recently, evidence for a molluscan affinity has been accumulating, based on new details of Wiwaxia's mouthparts, scales, and growth history.
The proposed clade Halwaxiida contains Wiwaxia as well as several similar Cambrian animals.